Public conveyances, such as rail cars, buses, elevators, and the like, are typically subject to government regulations requiring that a passenger compartment of the conveyance be at least partially constructed from fire retardant panels, which provide protection for occupants of the compartment in the event that a fire should occur outside or within the passenger compartment.
For example, in the past, passenger rail cars and buses have sometimes utilized a flooring system in which floor panels, approximately three-quarters of an inch thick, are mounted to the top side of a floor-supporting underframe. Typically the floor panels have been attached to the underframe by various methods, including adhesive bonding, or fastening with screws or other fasteners. The underframe has typically been deep enough to allow a layer of insulation material (usually glass wool, fiberglass, or rock wool), to be laid upon the top surface of a series of thin steel sheets that are then welded to the bottom side of the underframe, to form an underpan assembly. The underframe is sometimes configured to be deep enough that there is an air gap provided between the underside of the floor panel and the insulation material on the top side of the steel underpan. The air gap serves as an insulation zone for heat transfer, in the event of a fire beneath the transit vehicle. Typically, in North America, such a floor structure is required to pass a fire endurance test for passenger fire safety, in which a completed flooring system is mounted over a pit in which a gas burner is located to simulate a fire beneath the vehicle. During the fire test, weights are placed on the top surface of the floor panels, to simulate a typical live floor loading resulting from carrying passengers.
In one common form of a floor panel, used in prior flooring systems for mass transit vehicles, a plywood sheet is sandwiched between, and bonded to, the interior surfaces of two stainless steel or aluminum sheets. This construction results in floor panels that are heavier than is desirable. Also, past experience has shown that, during operation of the mass transit vehicle, the plywood core sometimes is exposed to water, which causes the stainless steel or aluminum sheets to delaminate and the plywood panel to rot.
U.S. Pat. No. 6,824,851, which is assigned to the Assignee of the present invention, and is hereby incorporated in its entirety herein by reference, discloses an approximately three-quarter inch thick phenolic composite flooring system for mass transit vehicles, which provides significant improvement over flooring systems utilizing floor panels having stainless steel or aluminum sheets bonded to the faces of a plywood panel. By virtue of its construction, the phenolic composite flooring system disclosed in U.S. Pat. No. 6,824,851 is considerably lighter in weight than flooring systems utilizing plywood panels clad with stainless steel or aluminum sheets. Also, the flooring system of the '851 patent provides greater ability, than flooring systems using floor panels having a plywood sheet clad with stainless steel skins, to withstand harsh environmental conditions, such as exposure to water or moisture.
Although use of a phenolic composite flooring system, according to U.S. Pat. No. 6,824,851, in a traditional mass transit vehicle constructions, having an insulation material laid on the top surface of thin steel sheets welded to the bottom of a steel underframe to form an underpan assembly, have been shown to provide significant advantages over similar systems utilizing metal clad plywood floor panels, further improvement is desirable.
It is desirable to eliminate the insulation and heavy steel underpan, to reduce weight and complexity of the transit vehicle, and to eliminate the cost of the insulation, the steel underpan, and costs incurred in installing the insulation and underpan onto the underframe of the vehicle, while still providing sufficient flame retardant capability to meet governmental regulations.
Past experience has also shown that use of the air gap and steel underpan in previous mass transit vehicles created a cavity between the underpan and the floor panels which “drummed” during use of the mass transit vehicle. Elimination of the underpan and air gap would also eliminate the cavity, and potentially lead to a quieter passenger cab environment.
It has also been observed that previous, conventional underpan and underframe assemblies, would, from time-to-time, trap water between the bottom of the floor panel and the top side of the underpan. In some instances, large amounts of standing water would be trapped within the cavity between the underpan and the floor panels. As noted above, this standing water sometimes damage the floor panels, and could amount to significant dead weight which had to be carried by the mass transit vehicle.
It is desirable, therefore, to provide an improved fire retardant panel apparatus, and a method of making and using such an improved fire retardant panel apparatus, in a form which addresses one or more of the disadvantages of prior flooring systems for mass transit vehicles. It is further desirable to produce a fire retardant panel for use in other conveyances such as elevators and marine vessels. It is further desirable to provide an improved fire retardant panel, and panel apparatus, for use in defining one or more of the floor, ceiling, and/or walls of a conveyance for transporting passengers or other cargo.